The present invention relates to a rolling block for rolling metallic bars or wires. More particularly, it relates to a rolling block having a number of rolling frames arranged at successive frame spots and each provided with three rollers arranged in star-like fashion and displaceable radially to a longitudinal axis of the rolling product, and separate regulatable motors for driving the rollers of the rolling block and all roller frames with finishing passes are always located at the last frame spots at the outlet side and are driven there by at least one rear motor.
In a known rolling block of this type which is disclosed, for example, in the German patent DE-PS 34 45 219, all drawing passes at the inlet side are driven jointly by a first motor while both finishing passes at the outlet side are driven respectively by a second or a third motor. Drawing passes are the passes which are arranged at the front and central frame spots of the rolling block and in which a great cross-section reduction of the rolling product is performed or can be performed. In contrast, the finishing passes are the passes which provide the desired final cross-section and the desired final dimensions of the rolling product at the outlet side frame spots and therefore deal with a relatively smaller cross-section reduction. Moreover, a construction is known in which the last finishing pass at the outlet side is driven by the second motor and both subsequent finishing passes are driven jointly by the third motor, wherein to the contrary the substantially greater number of the drawing passes are driven at the inlet side jointly by the first motor than in the previously described construction.
These known constructions have some disadvantages. During production of a substantially greater or smaller final cross-section from the same starting cross-section, or in other words always when the total cross-section reduction of the rolling block must be substantially changed and as a result in the rolling block another number of the drawing passes and rolling frames are required, one can fail to do it only at the first frame spots at the inlet side. The last frame spots at the outlet side must be provided with the rolling frames in the known constructions. The reason is that only these last frame spots are driven by the second or third motor and as a result only there the ratio of the roller rotary speeds of the neighboring rolling frames is steplessly changeable by the separate regulatable motors. The latter is required when it is necessary to change the cross-section reduction of the rolling product so that the final cross-section with all intermediate sizes can be produced. With a predetermined starting cross-section which must be maintained, it is necessary during a conversion, for example, to a substantially greater final cross-section, to use several previously utilized front drawing passes but not longer to use for example the last previously used drawing pass. Therefore it is removed with its rolling frame from the rolling block, in order to provide in the subsequent finishing caliber, which is greater due to the exchange, a greater rolling product cross-section corresponding to it. The released frame spot must be now provided with the drawing pass, which before preceded the last drawing pass and now becomes the last drawing pass. In other words, the associated rolling frame must be offset by one frame spot to the outlet side and also turned by 180.degree. around its drive axis, so that its roller gaps between the rollers are not arranged at the same peripheral portion of the rolling product as the roller gaps of the subsequent first finishing pass. This must be done with all other preceding and further used drawing calibers and their rolling frames, since fixed and uniform transmission ratios are provided between the drive shafts of the front and central frame spots, so that between the remaining drawing passes no frame spots can be released. Otherwise, the drive rotary speeds for both rolling frames before and after the released frame spot are not determined relative to one another. In this manner a substantial labor and time consumption is needed during a conversion of the rolling block to substantially greater or smaller final dimensions, when at least one redundant drawing pass or rolling frame is removed or an additional one must be introduced and all preceding drawing passes are offset by at least one spot.